Embossing method



Aug. 16, 1966 E, MITTMAN 3,266,416

EMBOSSING METHOD Filed Dec. 10, 1964 30 28 22 24 22 2 28 30 28 30 28 30 22 24 r 28 W, WW m 2 P ---l F/G. 2 1 FILM T0 BE EMBOSSED EMBOSSED FILM BACK- UP ROLL INVENTOR. FIG. 3 EMANUEL mnmm AT TQRN EY on the material.

United States Patent 3,266,416 EMBOSSING METHGD Emanuel Mittman, Forest Hills, N.Y., assiguor to W. R. Grace & (30., New York, N.Y., a corporation of Connecticut Filed Dec. 10, 1964, Ser. No. 417,344 7 Claims. (Cl. 10132) This invention relates to embossing techniques and, more particularly, to a technique for embossing sheet material which provides a flat cylindrical roll of material for shipment and which prevents rippling in the sheet material .after subsequent unrolling.

In the embossing of sheet material, such as plastic film, to produce a pattern on the film, a problem is encountered when the sheet material is rolled to form a roll of material for shipment and when it is subsequently unrolled for use. In particular, the pattern embossed on the material produces a film of nonuniform thickness. When the film is thereafter rolled to form a roll of material, the nonuniformities in thickness may be so positioned within the roll that the surface of the roll is not fiat but is characterized by depressions and elevations across the roll corresponding to superimposed portions of the film containing the same subpatterns. This rippling in the surface of the roll is undesirable because it presents handling problems. Further, because the sheet material is typically impressionable and compressible, the rippling normally remains in the sheet material after it is subsequently unrolled for use, presenting a poor product.

To avoid such irregularities in the surface of a roll of material and in the sheet material after unrolling, it is possible to shift the embossed material slowly back and forth in a transverse direction so that the same subpatterns are not superimposed when a roll of material is produced for shipment. The transverse movement of the embossed material may be achieved ahead of fixed cutting blades or slitters which trim. the embossed material to a uniform width. There are two disadvantages with this type of arrangement. First, the transverse shifting of the material would normally be carried out by angularly displacing the material as it exits from the embossing station. A considerable distance between the embossing station and the trimming station is required, however, to translate the angular shift of the material to a transverse shift without wrinkling the material. Second, because the material is shifted transversely ahead of the cutting blades, its width must be increased by an amount at least as great as the distance of shifting to ensure that 'both edges of the material are trimmed by the cutting blades to produce a finished product of uniform width. This increase in untrimmed product width represents waste which increases the cost of the finished product.

An alternative arrangement is to shift the trimming blades back and forth along an axis transverse to the movement of the embossed material while retaining the embossed material fixed in the transverse direction. This effectively shifts the transverse location of the pattern The disadvantages with this type of arrangement are that the width of the embossed material must be increased to account for the shifting of the trimming blades and that the windup roll which rolls up the material must be concurrently shifted to form a proper roll with flat ends.

A still further alternative arrangement is to trim the material to its finished width before it is embossed and to shift the material back and forth in the transverse direction as it is embossed so as to shift the pattern in the transverse direction on the finished sheet. Concurrently, the windup roll must be shifted in accordance with Patented August 16, 1966 "ice the material shifting to form a proper roll of material with flat ends. The disadvantages with this arrangement are that proper synchronizing between material shifting and windup must be achieved, and that the trimming of the material is not done at the end of the process. It is desirable to trim to a finished width at the end of the process to allow for defects which are likely to occur along the edges of the material.

The present invention overcomes these disadvantages and provides a flat cylindrical roll of embossed material for shipment and an unrippled sheet of material after unrolling for use 'by moving the embossing roll in a direction transverse to the direction of movement of the material as it passes through the embossing station. In particular, the embossing roll is typically oscillated along an axis in the transverse direction at a relatively slow rate so as to slowly shift the pattern formed on the material. The shifting of the pattern is sufficient to prevent the elevations and depressions in the surface of the material that produce the pattern from being superimposed in the roll of material. Hence a ripple in the roll of material is avoided, producing a fiat cylindrical roll, thereby avoiding a rippled sheet of material after subsequent unrolling for use. At the same time the transverse shifting of the pattern is such as to be relatively slight with respect to a piece of material of ordinary length, so that for such a piece a uniform pattern without any noticeable transverse shift is produced. By this technique, increased production line length and increased width of untrimmed sheet material are avoided, among other difliculties as noted above.

The invention will be more completely understood by reference to the following detailed description, which includes the appended drawings, in which:

FIG. 1 is a perspective view of a sheet of embossed material being rolled for shipment;

FIGS. 2 and 2A are typical profiles of embossed sheets of material; i.e., each profile is a sectional view of an embossed sheet taken across the width of the sheet; and

FIG. 3 is a perspective view of a sheet of material being embossed in accordance with the invention.

Referring to FIG. 1, a sheet of embossed material 10 is shown moving in the direction of arrow 12 and rolled onto a windup roll 14 which is rotated as shown by arrow 16. As a roll of material is formed, the surface of the roll may not be flat but may be rippled as shown in FIG. 1 containing elevations 18 and depressions 20, for

example. The rippling of the roll is undesirable, because .be noted from the figure, the overall pattern is characterized by elevations or plateaus 22 and corresponding depressions or valleys 24 which together form a subpattern 25. Two of such subpatterns are shown in FIG. subpattern 26 is embossed on the sheet between each of the subpatterns 25 and is characterized by closely spaced peaks 28 and intermediate valleys 30. The width of each of the patterns 25 is designated d while the width of each pattern 26 is designated d As shown, d is greater than d although this is purely arbitrary. When a sheet of material having a profile such as that shown in FIG. 2 is wrapped about itself to form a roll as shown in FIG. 1, the peaks 22, for example, are normally superimposed so that the finished roll is itself formed with peaks, as des- 3 ignated 18 in FIG. 1. Similarly, valleys such as 30 shown in FIG. 2 are normally superimposed to form valleys in the roll, as designated 20 in FIG. 1.

FIG. 2A is a profile of an embossed sheet of material similar to the profile of FIG. 2. Unlike the profile of FIG. 2, which presents a smooth back surface 29, the profile of FIG. 2A presents an irregular surface on each side of the sheet. The profile of FIG. 2A includes repetitive portions 31 and 33, of different heights, which may become superimposed in a finished roll to create a ripped roll having the disadvantages pointed out above in connection with FIG. 1.

As explained before, the embossed sheet may be moved back and forth in a transverse direction prior to being trimmed to a uniform width so that the pattern on the finished sheet is shifted transversely to prevent the peaks and valleys in the pattern from being superimposed when a roll is formed. There are two primary disadvantages of this shifting of material. First, the shifting is typically carried out by angularly shifting the film, i.e., by changing its direction of movement. A relatively long space, however, must be provided between the point at which the material is shifted and the trimming station so that the material may be made to travel in a direction perpendicular to a line joining the leading edges of the trimming blades without causing wrinkling of the material. If such a space were not provided, the material could not be made to travel in the proper direction without wrinkling and a properly trimmed product would not result. This increased .space increases the length of the production line, which is undesirable from the standpoint of requiring additional space in a factory. Second, because the material is shifted, the width of the product arriving at the trimming station must be greater than the trimmed width by an amount at least as great as the distance through which the material is transversely shifted. This results in a large amount of waste material which must be properly embossed but which does not end in a finished product.

As an alternative technique, the slitters in the trimming station could be concurrently shifted back and forth in the transverse direction. Although this would shift the transverse location of a pattern on a finished sheet of material, an increased width of material prior to trimming is required. Additionally, the windup roll must be concurrently shifted with the trimming blades to form a proper roll of material whose ends are flat. Without the shifting of the windup roll, the roll of material would not be built up over a single portion of the windup roll. The requirement of synchronizing the shifting of trimming blades and a windup roll requires coupling arrangements which may be diflicult to construct.

A still further technique to provide the shifting of a pattern on a finished strip of material is to first trim the material, and then to shift it transversely back and forth while passing through an embossing station. Concurrently, the windup roll would have to be shifted so that a proper finished roll with fiat ends is produced. Such a technique, while eliminating the loss of extra material as in the above techniques, still requires an increasedproduction line length to achieve the material shifting, and also requires the concurrent shifting of the windup roll. Synchronizing the shifting of material and a roll may present problems in the construction of suitable machinery. Further, trimming the material in the process prior to emhossing is not desirable, inasmuch as the edges of the material may become damaged during later steps. Trimming is most advantageously left to the end of the process.

FIG. 3 shows the technique employed in the present invention for shifting the pattern on a sheet of finished embossed material to prevent the finished roll of material from being rippled as in FIG. 1, but without requiring any transverse shifting of the material or concurrent shifting of trimming blades and windup roll or trimming prior to the end of the process. Sheet 10 is shown conveyed in the direction of arrows 32 between an embossing roll 34 and a backup roll 36 which are rotated in the directions of arrows 38 and 40, respectively, by any suitable driving means (not shown). The embossing roll contains a pattern thereon which embosses the sheet 10 so as to produce a transverse profile such as shown in FIG. 2, for example. The embossing roll is oscillated transversely with respect to the direction of film movement, as illustrated by arrow 42, by any suitable driving means (not shown). The transverse movement of the embossing roll is typically much slower than the movement of the sheet 10 through the embossing and backup rolls. In this fash ion the pattern on the sheet 10 produced by the embossing roll 34 is shifted transversely and when the film is rolled as shown in FIG. 1 no ripples in the surface are present and a fiat cylindrical roll of material is produced. At the same time the pattern shift is not noticeable to the eye. For example, the total oscillating movement of the embossing roll 34 may be inch for every inches of material passing by the embossing roll.

By moving the embossing roll 34, a sheet of a width only slightly greater than the width of the finished product can be presented to the trimming station, thereby eliminating the waste material necessitated by a transverse movement of material or trimming blades and windup roll. As a result, a wider sheet of finished material usable by a customer is produced by this technique from equipment that produces sheet material of a given width to be embossed.

Further, increased production line length is not required as in the case of angularly shifting the direction of material movement.

If desired, the backup roll 36 may be oscillated transversely with respect to the direction of movement of the film 10, as shown by arrow 44. This movement of the backup roll, achieved by any suitable driving means (not shown), may be desirable to prevent the roll from being defaced by the embossing roll when certain portions of the pattern on the embossing roll are caused to press against the same portions of the backup roll. The backup and embossing rolls would be oscillated at different rates normally so as to prevent such defacing of the backup roll.

The transverse movement of the embossing roll is typically the same as the distance between the widest spaced adjacent and identical subpatterns. For example, in FIG. 3 the total transverse movement of the embossing roll 34 would be equal to the distance d In a typical pattern, this distance might be 2 /2 inches. For an oscillating movement of inch for every 180 inches of sheet movement, a subpattern 2 /2 inches Wide would be shifted transversely 2 /2 inches every 7,200 inches or every 600 feet of material. This shift is not noticeable in sheets of material of ordinary length in use, such as a 10-foot shower curtain in which the shift is inch. By this movement, however, the overall pattern on the film composed of repetitive subpatterns is shifted sufiiciently so that the roll of material produced for shipment is fiat on its outer surface.

It will be appreciated that the invention provides a method of embossing a sheet of material to aid in the fabrication of a uniform roll of a finished product, which also prevents rippling in the sheet material after it is unrolled for use. It will be understood that various modifications of the technique disclosed may be made which nonetheless fall within the scope of the invention.

Accordingly, the invention should be taken to be identified by the following claims.

What is claimed is: 1. A method for preparing an embossed sheet material which comprises:

(1) moving a continuous sheet of material in a path between a pair of rotary embossing members, and (2) simultaneously moving at least one of said embossing members in a direction generally transverse to the path or direction of said material while said material is maintained in said path.

2. The method of claim 1 wherein one of said embossing members oscillates in a direction generally transverse to the path or direction of travel of said material.

3. The method of claim 1 wherein said embossing member moves in a direction generally transverse to the direction of movement of said material at a rate which is substantially less than the rate at which the material is moving.

4. The method of claim 1 wherein one of said embossing members moves in the direction generally transverse to the direction of movement of said sheet while the other member remains substantially motionless in said transverse direction.

5. The method of claim 1 wherein both of the embossing members move in a direction generally transverse to the direction of movement of said material and each member moves in a direction opposite to that of the other.

6. The method of claim 1 wherein both of said emboss- 20 7. The method of claim 2 wherein the movement of the embossing member in one cycle of oscillation is generally the same as the transverse distance between repetitive subpatterns on the embossing member.

References (Iited by the Examiner UNITED STATES PATENTS 289,480 12/1883 White 101-9 1,119,730 12/1914 Speed 10123 1,231,697 7/1917 Brown 101-32 References Cited by the Applicant UNITED STATES PATENTS 434,539 8/ 1890 Ecaubert.

560,479 5/ 1896 Crepet. 1,325,529 12/ 1919 Oberley. 2,746,387 5/ 1956 Neumann. 3,019,723 2/ 1962 Bauer.

ROBERT E. PULFREY, Primary Examiner.

W. MCCARTHY, Assistant Examiner. 

1. A METHOD FOR PREPARING AN EMBOSSED SHEET MATERIAL WHICH COMPRISES: (1) MOVING A CONTINUOUS SHEET OF MATERIAL IN A PATH BETWEEN A PAIR OF ROTARY EMBOSSING MEMBERS, AND (2) SIMULTANEOUSLY MOVING AT LEAST ONE OF SAID EMBOSSING MEMBERS IN A DIRECTION GENERALLY TRANSVERSE TO THE PATH OR DIRECTION OF SAID MATERIAL WHILE SAID MATERIAL IS MAINTAINED IN SAID PATH. 